I really hate booting into Windows 7 just to boot up Ps to cut out some stuff and then flip back to Ubuntu... plus, if i missed something or other, its a mega pain in the ass to reboot again.
Gimp also doesn't work well for this at all.
As just Tom said, you will have to find a VM. The choices avaliable are:
KVM: It's the 'new' virtualization, it comes with the kernel. You have to install a single application and you can either manage your virtual machine by console or you can do this with 'libvirt' (virt-manager). (3D support is the same as Virtualbox, read below. It's not really good so some operations may be slower than on Windows due to the lack of openGL accel.)
VMWare Workstation: Commercial software, not really cheap but the best. It provides stable, excellent 3D performance, awesomeness when it comes to Photoshop (since I also do some graphical work when I have to and Workstation just does what I want.)
VirtualBox: Free virtualization software by Oracle (cough Sun). It's not the best, the 3D is very buggy (it's just a hack from/by Wine sadly), but it's free. Give it a spin and see whether it does the job or not. For me, I experienced too many bugs to stay with VirtualBox.
Parallel Workstations: A good virtualization software again. However, I never had a chance to test it for a very long time.
Oh how could I forgot VMWare Player. Nowadays it's just like a free VMWare Workstation. Back then you couldn't make guests with it, but it's all solved now. Also you can just grab guest images from the web from sites like this.
Why not run Windows in a Virtualbox VM? That gets rid of the reboot problem completely.
Since you're doing web development, you could make the VM run a Windows server instead, which would also give you an always-available server for testing.